1. Field of the Invention
The present invention relates to a display substrate, a method of manufacturing the display substrate and a display device having the display substrate. More particularly, the present invention relates to a display substrate capable of improving display quality of an image, a method of manufacturing the display substrate and a display device having the display substrate.
2. Description of the Related Art
Generally, a display device converts information processed from an information processing device to an image.
Examples of the display devices include a cathode ray tube (CRT) type display device, a liquid crystal display (LCD) device, an organic light emitting display (OLED) device, etc.
Liquid crystal display (LCD) devices are classified into three types, a transmissive type LCD device, a reflective type LCD device, and a reflective-transmissive type LCD device, depending upon the method of using light.
The transmissive type LCD device displays an image using light provided from an internal lamp installed within the LCD device. The reflective type LCD device displays an image using light externally provided (e.g., from the sun, a lamp, or other illuminating device). The reflective-transmissive type LCD device displays an image using light internally provided from a lamp installed in the LCD device and/or externally provided.
The transmissive type LCD device includes a transparent electrode that is transparent and conductive, while the reflective type LCD device includes a reflective electrode that has a greater reflectivity than a transparent electrode. The reflective-transmissive type LCD device includes both a transparent electrode and a reflective electrode.
When the reflective electrode of the reflective type LCD device or the reflective-transmissive type LCD device includes aluminum or aluminum alloy having a high reflectivity (e.g., reflective electrodes made of aluminum or of aluminum alloy), hillocks may be formed on the surface of the reflective electrode (e.g., during a curing process for an alignment layer formed on the reflective electrode), and galvanic corrosion may occur between the reflective electrode and the transparent electrode.
Aluminum films are remarkably good for fabricating electrodes and lines because of their low resistivity, low cost, high adhesion, and superior patternability. However, the thermal expansion mismatch between Al films and a substrate or layer of display panels produces a large compressive stress in the Al films upon heating, and results in the formation of hillocks (or whiskers) in order to relieve the stress.
In order to prevent the galvanic corrosion problem, a corrosion-proof layer may be formed between the reflective electrode and the transparent electrode. However, formation of the corrosion-proof layer requires a great increase in the number of manufacturing steps in a manufacturing process, which increases manufacturing costs.